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Background. Enormous diversities exist regarding shape, number, and arrangement of the olfactory lamellae, distribution of the sensory and non-sensory epithelium as well as the abundance of various receptor cells among different teleosts. This study was aimed at describing the morphology, histology and SEM ultrastructure of the olfactory epithelium of a spotted snakehead fish, Channa punctatus (Bloch, 1793). Materials and Methods. OE of C. punctatus was examined through LM and SEM. Results. Olfactory epithelium of C. punctatus containing 18 to 20 lamellae provides a large surface area. Sensory epithelium possesses both ciliated and microvillous olfactory receptor cells (ORC), which are intermingled and distributed throughout the epithelium. ORCs are arranged in alternate rows with supporting cells (SCs). ORC is columnar cell with a round cell body, an axonal process and a long dendrite. The apical surfaces of the ORCs are provided either with 10–12 cilia or numerous microvilli and the SCs with fingerprint like microridges. ORCs with rod-shaped dendrite ending were found in small numbers. Non-sensory epithelium is composed of ciliated nonsensory cells (cNSC) and covered with a dense carpet of cilia, which help in ventilating the olfactory chambers. Conclusion. A large surface area of OE, the high density of both ciliated and microvillous ORC and adequate arrangement for ventilating the olfactory chambers indicate that C. punctatus is very much dependent on its olfactory sense.
Exposure of the freshwater catfish H. fossilis to an acute concentration of 0.20 mg dm-3 (l/5th of 4 days LC50) of malachite green for 4 days evoked hepatic and muscle glycogenolysis with concomitant hyperglycaemia and chloraemia. Exposure of fish to sub-acute 0.10 mg dm-3 (l/10th of 4 days LC50) and sub-lethal 0.05 mg dm-3 (l/20th of 4 days LC50) concentrations of the dye also evoked a significant increase in blood glucose and chloride levels at short (10-20 days) and long (30-60 days) term as well as liver and muscle glycogenolysis at short term. However, there were no marked changes in the liver glycogen content at the sub-lethal dose or muscle glycogen content at either sub-acute or sub-lethal concentrations for long term exposure.
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